For general AOEs, I've not had an issue when using a controller, and I play on an American datacentre while living in Europe. Might we worth trying it out with a controller? You say that it's usually fine, but you should be able to step outside of the vast, vast majority of AOEs.
The main reason that the Drop Dead DRG is a thing is because of Jump attacks. You can never know when a boss is about to drop an AOE on you, and the animation lock for the Jump attacks is such that after you launch, the AOE can drop, and by the time you land back down and try to get out of the AOE, it's too late.
That's just the way the job works in the game. You can only try to mitigate it so much before you're losing DPS, so it's better to take the damage, hope you survive it, and let a healer fix you up.
I tend to switch between controller (Solo Adventuring) and K+M (Dungeons and Raids) depending on the amount of precision I need. I have been trying out the Legacy controls today, they've been helping me out a bit, once I got over the camera differences.
The Jump lock, I feel that pain. Well, at least it's not
unexpected of me to be on my face occasionally, I'll just have to be aware of it.
~*~
On another note, finally got to floor 50 of PotD. Ended up doing it in a randomized party, and from 1-40 it was smooth sailing. But 41-50 took like 5 tries. 1st round we were wiped on floor 45, whatever, it can happen. But the next 3 rounds I got floor 49 and a couple of my teamates just bum rushed into a horde of enemies, despite us unlocking the way forward. I have a feeling they may have been doing it on purpose, because they didn't get enough Aether or something? Is this a common occurrence, or am I just crazy? I wish I could have asked them, but I don't speak Japanese. Regadless, incredibly frustrating, seeing as I just wanted to unlock the ability to trade in weapons.
I think the most successful runs in that dungeon are always those with a tank. Everyone by default seems to just follow the tank, targeting who they target. Makes for better teamwork, even without any communication.